Study: 92 Percent of Out-of-Hospital Cardiac Arrest Victims Die

The majority of people who experience an OHCA event do not receive bystander-assisted cardiopulmonary resuscitation or other timely interventions that improve the likelihood of survival to hospital discharge.

Jul 31, 2011

According to a new study, out-of-hospital cardiac arrest (OHCA) is a leading cause of death among adults in the United States. Approximately 300,000 OHCA events occur each year in the U.S., and approximately 92 percent of people who experience an OHCA die. The study, published in CDC’s Morbidity and Mortality Weekly Report, provides surveillance data on OHCA events that occurred in the U.S. from Oct. 1, 2005, to Dec. 31, 2010.

OHCA is defined as cessation of cardiac mechanical activity that occurs outside of the hospital setting and is confirmed by the absence of signs of circulation. Whereas an OHCA can occur from noncardiac causes (i.e., trauma, drowning, overdose, asphyxia, electrocution, and primary respiratory arrests), the majority (70-85 percent) of such events have a cardiac cause.

The majority of people who experience an OHCA event do not receive bystander-assisted cardiopulmonary resuscitation or other timely interventions that improve the likelihood of survival to hospital discharge (e.g., defibrillation). Because nearly half of cardiac arrest events are witnessed, efforts to increase survival rates should focus on timely and effective delivery of interventions by bystanders and emergency medical services (EMS) personnel.

In the first few minutes following OHCA, swift implementation of five critical actions by bystanders or EMS providers can substantially increase the chances of survival. These actions should be undertaken regardless of the cause of OHCA and include 1) rapid activation of EMS by calling 911, 2) rapid initiation of cardiopulmonary resuscitation (CPR), 3) prompt application and use of an automated external defibrillator (AED), 4) rapid delivery of advanced life support by EMS providers, and 5) early post-resuscitative care. Despite decades of research, median reported rates of survival to hospital discharge are poor (7.9 percent) and have remained virtually unchanged for three decades. Moreover, survival rates vary widely across the United States. The likelihood of surviving an OHCA caused by ventricular fibrillation varies widely (range: 2 to 35 percent), depending on the location of the OHCA event.

Approximately 36.7 percent of OHCA events were witnessed by a bystander. Only 33.3 percent of all patients received bystander CPR, and only 3.7 percent were treated by bystanders with an AED before the arrival of EMS providers. People most likely to survive OHCA are those who are witnessed to collapse by a bystander and found in a shockable rhythm (e.g., ventricular fibrillation or pulseless ventricular tachycardia).

According to the study, the mean age at cardiac arrest was 64 years old, and 61.1 percent of people who experienced OHCA were male. According to local EMS agency protocols, 21.6 percent of patients were pronounced dead after resuscitation efforts were terminated in the pre-hospital setting. The survival rate to hospital admission was 26.3 percent, and the overall survival rate to hospital discharge was 9.6 percent.

This is the first report to provide summary data from an OHCA surveillance registry in the United States.